The polyphenylene ether resins, also frequently referred to as polyphenylene oxide resins, constitute a family of engineering thermoplastics known to be moldable or extrudable into a wide variety of articles ranging from parts or housings for household appliances or furnishings to essential components in various industrial applications. The polyphenylene ether resins and methods of their preparation are described in the patent literature, including U.S. Pat. Nos. 3,306,874 and 3,306,875 (Hay), and U.S. Pat. Nos. 3,257,357 and 3,257,358 (Stamatoff).
The polyphenylene ether (oxide) resins are admixable in widely variant proportions with styrene resins and other alkenyl aromatic polymers, including high impact (rubber modified) polystyrene resins, as is known from the disclosure in U.S. Pat. No. 3,383,435 (Cizek), and elsewhere in the literature.
The terms "high impact Polystyrene" and "rubber modified high impact polystyrene" have been employed in the art to refer to a family of polystyrene resins which are modified during manufacture to reduce the brittleness by incorporating a rubber during or after styrene polymerization. This group of materials are sometimes referred to simply as "HIPS". Various methods for their production are known. One process, which is described in British Pat. No. 1,002,901 (Westphal and Heinig), involves the polymerization of styrene monomer in the presence of a polybutadiene rubber or, alternatively, a polystyrene-polybutadiene (GR-S)rubber.
Recent advances in the art have shown that compositions of polyphenylene ether resin and styrene homopolymers or copolymers can be obtained by polymerizing a styrene monomer in the presence of a previously formed polyphenylene ether resin to form a graft copolymer of the two. Numerous procedures of this general type are described in the patent literature, including U.S. Pat. No. 3,664,977 (Nakanishi, et al.), U.S. Pat. No. 3,700,750 (Yamanouchi, et al.), U.S. Pat. No. 3,939,930 (Izawa, et al.), U.S. Pat. No. 4,189,417 (Goossens), and German patent publication No. 1,939,033 (Hamada, et al.). Typically, the reactions are carried out using the styrene as the solvent, and frequently in the presence of a catalyst such as a free radical initiator. The Nakanishi, et al. process includes a rubber as an integral component of the copolymerization reaction. Izawa, et al. and Yamanouchi, et al. also disclose embodiments in which the graft polymerization is conducted with a rubber present.
Allan Hay, in U.S. Pat. No. 3,402,144, proposes that polyphenylene ether resins can be modified by treatment with alkali metal alkyls or aryls to provide an activated polymer which will readily react with anionically polymerizable monomers to produce graft copolymers. Bostick, et al. in U.S. Pat. No. 3,522,326, describe graft copolymers of a 2-8 carbon alkylene and a polyphenylene ether prepared by this means, and they indicate that other monomers, including styrene, can also be grafted onto the polyphenylene ether using the same procedure.
Another recent development, disclosed in U.S. Pat. No. 4,152,369 (Bennett, et al.), comprises a process in which an alkenyl aromatic monomer, for example, styrene, is used as a solvent for the oxidative coupling of a phenol to form a polyphenylene ether resin and, thereafter, the alkenyl aromatic monomer is also polymerized to form what is described as a blend of the two polymers.
Olander in U.S. Pat. No. 4,207,406 describes the formation of polyphenylene oxide copolymers having alkenyl substituents in the structure and proposes that butadiene monomer, styrene monomer or polybutadiene can be interreacted to produce a graft copolymer.